Magnetic tunnel junctions with coupling - pinning layer lattice matching

ABSTRACT

Embodiments of magnetic tunnel junction (MTJ) structures discussed herein employ a first pinning layer and a second pinning layer with a synthetic anti-ferrimagnetic layer disposed therebetween. The first pinning layer in contact with the seed layer can contain a single layer of platinum or palladium, alone or in combination with one or more bilayers of cobalt and platinum (Pt), nickel (Ni), or palladium (Pd), or combinations or alloys thereof, The first pinning layer and the second pinning layer can have a different composition or configuration such that the first pinning layer has a higher magnetic material content than the second pinning layer and/or is thicker than the second pinning layer. The MTJ stacks discussed herein maintain desirable magnetic properties subsequent to high temperature annealing.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Patent ApplicationNo. 62/676,119, “Magnetic Tunnel Junctions with Coupling-Pinning LayerLattice Matching,” filed May 24, 2018, and is incorporated by referenceherein in its entirety.

BACKGROUND Field

Embodiments of the present disclosure generally relate to fabricatingmagnetic tunnel junction structures for magnetic random access memory(MRAM) applications.

Description of the Related Art

Spin transfer torque magnetic random access memories, or STT-MRAMs,employ magnetic tunnel junction structures in the memory cells thereof,wherein two ferro-magnetic layers are spaced from one another by a thininsulating or “dielectric” layer. One of the magnetic layers has a fixedmagnetic polarity, the other has a magnetic polarity which isselectively changeable between two states. Where the magnetic layershave perpendicular magnetic anisotropy, the polarity of the changeablepolarity layer can be switched between having the same polarity as thefixed polarity layer, or the opposite polarity to that of the fixedpolarity layer, in the depth direction of a stack of film layersincluding the magnetic tunnel junction or “MTJ” structure. The electricresistance across the MTJ is a function of the polarity of thechangeable polarity layer with respect to the fixed polarity layer.Where the polarities of the two layers are the same in the depthdirection of the MTJ, the electric resistance across the MTJ is low, andwhen they are opposite to one another in the depth direction of the MTJ,the electric resistance across the MTJ is high. Thus, the electricalresistance across the cell can be used to indicate a value of 1 or 0,and thus store a data value, for example by using the low resistancestate as having the data value of 1, and the high resistance state asthe data value of 0.

To form an MTJ stack, a film layer stack is fabricated that includes afirst pinning layer and a second pinning layer and a syntheticanti-ferrimagnetic coupling (SyF) layer in between the first pinninglayer and the second pinning layer. The SyF coupling layer causessurface atoms of the first pinning layer and the second pinning layer,when exposed to a magnetic field, to align with surface atoms of the SyFcoupling layer, thereby pinning the orientation of the magnetic momentsof each of the first pinning layer and the second pinning layer. Thefirst pinning layer and the second pinning layer each include similarmagnetic moments, and will thus react similarly when an externalmagnetic field is applied to the conventional MTJ stack 100A. The SyFcoupling layer maintains an anti-parallel alignment of the magneticmoments of the first and second pinning layers.

Where MTJs employ synthetic anti-ferrimagnet (SyF) layers that includetwo or more ferromagnetic layers separated by a nonmagnetic layer, SyFcoupling can be lost after high temperature processing thereof, forexample processing at temperatures at or above about 400° C. Further,dipole fields can be created when a magnetic field is applied to the MTJstack, magnetic dipoles are closed circulations of electric current, anddipole fields can interfere with the performance of the MTJ stack,including the magnetic storage layer of the MTJ stack.

Thus, there remains a need for an improved MTJ stack that can withstandprocessing temperatures and reduces the dipole field effect.

SUMMARY

The present disclosure generally relates to the design and fabricationof magnetic tunnel junction (MTJ) stacks used for memory cells.

In one example, a device comprising: a magnetic tunnel junction stackincludes a first pinning layer comprising a first bilayer and a firstlattice-matching layer formed over the first bilayer, wherein the firstlattice-matching layer includes platinum or palladium. The MTJ stack ofthe device further includes a synthetic anti-ferrimagnetic (SyF)coupling layer in contact with the first lattice-matching layer of thefirst pinning layer; and a second pinning layer in contact with the SyFcoupling layer. The second pinning layer includes a secondlattice-matching layer formed from platinum or palladium, the secondlattice-matching layer being in contact with the SyF coupling layer.

In one example, a magnetic tunnel junction stack includes: a firstpinning layer comprising a first plurality of bilayers and a firstlattice-matching layer formed over the first plurality of bilayers,wherein the first lattice-matching layer comprises platinum orpalladium, and wherein each bilayer of the first plurality of bilayerscomprises a first cobalt interlayer and a second interlayer of platinum,nickel, palladium, or alloys or combinations thereof; a syntheticanti-ferrimagnetic (SyF) coupling layer formed on the first pinninglayer; and a second pinning layer formed on the SyF coupling layer,wherein the second pinning layer comprises a second lattice-matchinglayer formed on the SyF coupling layer

In another example, a magnetic tunnel junction (MTJ) stack includes: abuffer layer; a seed layer formed over the buffer layer, the seed layerbeing formed from chromium; and a first pinning layer in contact withthe seed layer. The first pinning layer includes a first bilayer and afirst lattice-matching layer formed over the first bilayer, the firstlattice-matching layer being formed from at least one of platinum orpalladium. The first bilayer includes a cobalt interlayer and at leastone interlayer comprising platinum, nickel, or palladium. The MTJ stackfurther includes a synthetic anti-ferrimagnetic (SyF) coupling layerformed on the first pinning layer; and a second pinning layer formed onthe SyF coupling layer, wherein the second pinning layer comprises asecond lattice-matching layer formed on the SyF coupling layer, whereinthe second lattice-matching layer comprises platinum or palladium. TheMTJ stack further includes a structure blocking layer formed on thesecond pinning layer, wherein the structure blocking layer comprises atleast one of tantalum, molybdenum, or tungsten; a magnetic referencelayer formed on the structure blocking layer; a tunnel barrier layerformed on the magnetic reference layer; an a magnetic storage layerformed on the tunnel barrier layer.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentdisclosure can be understood in detail, a more particular description ofthe disclosure, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlyexemplary embodiments and are therefore not to be considered limiting ofits scope, may admit to other equally effective embodiments.

FIG. 1A is a schematic illustration of an example magnetic tunneljunction (MTJ) stack.

FIG. 1B is a flow diagram of a method of fabricating memory devicesincluding magnetic tunnel junction (MTJ) stacks of FIG. 1A and accordingto embodiments of the present disclosure.

FIG. 2A is a schematic illustration of an MTJ stack according toembodiments of the present disclosure.

FIG. 2B is a magnified view of the buffer layer of an MTJ stackaccording to embodiments of the present disclosure.

FIG. 2C is a magnified view of the first pinning layer of an MTJ stackaccording to embodiments of the present disclosure.

FIG. 2D is a magnified view of the second pinning layer of an MTJ stackaccording to embodiments of the present disclosure.

FIG. 2E is a magnified view of an example magnetic storage layer of anMTJ stack according to embodiments of the present disclosure.

FIG. 2F is a magnified view of an example capping layer of an MTJ stackaccording to embodiments of the present disclosure.

To facilitate understanding, identical reference numerals have beenused, where possible, to designate identical elements that are common tothe figures. It is contemplated that elements and features of oneembodiment may be beneficially incorporated in other embodiments withoutfurther recitation.

DETAILED DESCRIPTION

Embodiments of the present disclosure relate to magnetic tunnel junction(MTJ) stacks and STT MRAM memory cells and memories. Herein, the MTJstacks are incorporated in a film stack including upper and lowerelectrodes such that the MTJ stack is sandwiched therebetween the upperelectrodes and the lower electrodes. The MTJ stack can be patterned toform a plurality of individual memory cells used in a magneto-resistiverandom-access memory (MRAM). In each MTJ stack of an MRAM cell there aretwo magnetic layers, wherein one magnetic layer has a fixed polarity andthe other has a polarity that can be switched by imposing a voltageacross the layer or by applying a current to that magnetic layer. Theelectrical resistance across the MRAM changes based on the relativepolarity between the first and second magnetic layers. The first andsecond magnetic layers are referred to herein as a magnetic referencelayer and a magnetic storage layer, respectively. The memory cellsformed from the MTJ stacks operate when there is a voltage imposedacross the cell or when there is a current passed through the cell. Inresponse to the application of voltage of sufficient strength, thepolarity of the switchable magnetic layer can be changed. Additionally,the resistivity of the cell can be determined by measuring the currentvs voltage relationship across the cell at a relatively low voltagebelow the threshold required to switch the magnetic polarity of themagnetic storage layer.

The basic MTJ stack discussed herein is formed using a plurality ofdeposition chambers to deposit thin film layers on a substrate, and,ultimately, to pattern and etch those deposited film layers. Thedeposition chambers used to form the MTJ stack discussed herein includephysical vapor deposition (PVD) chambers. Here PVD chambers are used toform the plurality of thin film layers of the MTJ stack. The MTJ stackincludes a buffer layer, a seed layer on the buffer layer, a firstpinning layer on the seed layer, a synthetic anti-ferrimagnetic (SyF)coupling layer on the first pinning layer, a second pinning layer on theSyF coupling layer, and a blocking layer on the second pinning layer. Inthe PVD operations described hereof, a plasma is formed of an inert ornoble gas such as argon (Ar), helium, (He), krypton (Kr), and/or xenon(Xe) in the sputtering chamber while the chamber is maintained in avacuum state. The PVD process chamber further contains at least onesputtering target and a substrate is disposed therein facing a generallyflat surface of the sputtering target. The sputtering target is coupledto a power supply such that the sputtering target is electrically drivento, or self establishes, a cathodic state in a circuit of the powersupply, through the plasma, to ground, for example a grounded portion ofthe sputtering chamber. The substrate is disposed on a pedestal or onanother structure in the sputtering chamber, the pedestal or otherstructure may be at a floating potential, connected to ground, or may bebiased to form an anode in the cathodic target to direct plasma to theanode or to the ground circuit. The positively ionized portion of theinert gas atoms in the sputtering chamber are electrically attracted tothe negatively biased target, and, thus, ions of the plasma bombard thetarget, which causes atoms of the target material to be ejected anddeposit on the substrate to a form a thin film composed of the targetmaterial(s) on the substrate.

In order to form a thin film of a compound, a sputtering targetincluding that compound can be sputtered using an Ar plasma in a PVDchamber. In another example, a plurality of sputtering targets is usedto deposit a compound layer on the substrate and each sputtering targetincludes one or more elements of the compound to be formed as a thinfilm on the substrate. The plurality of sputtering targets is present inthe PVD chamber and can be sputtered using Ar plasma or other gas basedplasma to form a desired compound layer on the substrate. Further, inthe PVD operations used herein to form layers of the MTJ stack,metal-oxides and metal-nitrides are formed using either a metal-oxidesputtering target or a metal-nitride sputtering target. In alternateembodiments, the metal-oxide or metal-nitride layers of the MTJ stackare formed in a PVD chamber by sputtering one or more sputtering targetscomposed of the metal of the metal oxide or metal nitride while Arplasma and either oxygen (O₂) or nitrogen (N₂) are present in the PVDchamber. In one example, a PVD chamber has a plurality of sputteringtargets disposed therein, each sputtering target in the PVD chamber isbiased by a power supply to establish a negative bias thereon, either bydirect application of a negative DC bias thereto, or by using a waveformto electrically drive or self-establish a cathodic state on the target,or combinations thereof. In this example, a shield inside the PVDchamber is configured to block one or more targets of the plurality oftargets from the plasma while allowing ions of the plasma formed in thePVD chamber to bombard at least one of the targets to eject or sputtertarget material atoms therefrom to form a thin film on the substrate. Inthis example, one or more sputtering targets are exposed to the Arplasma, and the sputtering thereof in series or simultaneously forms thedesired film composition on the substrate, and a separate PVD chamber isused to form metal-oxide and metal-nitride layers when O₂ or N₂,respectively, are used in addition to Ar plasma for film layer formationon the substrate.

A PVD system can include one or more PVD sputtering chambers coupled toa central robotic substrate transfer chamber. The central roboticsubstrate transfer chamber is configured to move substrates betweenloading stations coupled thereto and the sputtering chambers connectedthereto. The PVD system is kept at a base vacuum pressure of, forexample, 10 E⁻⁹ Torr, so that the substrate on which the MTJ stack isbeing formed is not exposed to an external atmosphere when the substrateon which the MTJ stack is being formed is moved among and between PVDchambers during fabrication of the MTJ film layer stack thereon. Priorto forming the initial film layer of the MTJ film layer stack on asubstrate, the substrate is degassed in a vacuum chamber and pre-cleanedusing an Ar gas plasma or in an He/H gas plasma in a dedicatedpre-cleaning chamber connected to the central robotic transfer chamber.During fabrication of the MTJ stack using the one or more PVD chambers,one or more noble or inert sputtering gases such as Ar, Kr, He, or Xecan be disposed in each of the PVD chambers. The gases are ionized toform a plasma in the chamber, and the ions of the plasma bombard thenegatively biased sputtering target(s) to eject surface atoms from thetarget to deposit a thin film of the target material(s) on a substratelocated in the PVD sputtering chamber. In an embodiment, a processingpressure in the one or more PVD chambers can be from about 2 mTorr toabout 3 mTorr. Depending upon the embodiment, the substrate supportpedestal (or other structure on which the substrate can be disposed) inthe PVD platform is held at from −200° C. to 600° C. during fabricationof at least the seed layer, the first and second pinning layers, the SyFcoupling layer and the buffer layer of the MTJ stack.

FIG. 1A is a schematic illustration of a magnetic tunnel junction (MTJ)stack. FIG. 1A shows a conventional MTJ stack 100A that includes asubstrate 102 including a conductive layer of tungsten (W), tantalumnitride (TaN), titanium nitride (Tin), or other metal layers thereof. Insome examples, the substrate 102 includes one or more transistors, bitor source lines, and other memory lines, previously fabricated thereinor thereon, or other elements to be used to form an MRAM memory andpreviously fabricated or formed thereon. The substrates on which the MTJstacks are formed can have dimensions including a diameter of less than200 mm, a diameter of 200 mm, a diameter of about 300 mm, about 450 mm,or another diameter, and may have a shape of a circle or a rectangularor square panel.

A buffer layer 104 in the conventional MTJ stack 100A is formed on thesubstrate 102 by sputtering one or more targets in a PVD chamber havingthe substrate therein, and here includes one or more layers ofCo_(x)Fe_(y)B_(z), TaN, Ta, or combinations thereof. A seed layer 106 isdeposited via sputtering in a PVD chamber over the buffer layer 104. Thebuffer layer 104 is used in the conventional MTJ stack 100A to improveadhesion of the seed layer 106 to the substrate. The seed layer 106 hereincludes platinum (Pt) or ruthenium (Ru) and is formed by sputtering atarget of Pt or Ru, or an alloy thereof, in a PVD chamber having thesubstrate therein. The seed layer 106 used to improve adhesion andseeding of subsequently deposited layers in the conventional MTJ stack100A by reducing or eliminating lattice mismatch between the bufferlayer 104 and the seed layer 106.

A first pinning layer 108 is formed on the seed layer 106 by sputtering.The first pinning layer 108 here includes a cobalt (Co) layer, one ormore Co-containing bilayers, or a combination of the cobalt layer andone or more Co-containing bilayers. A synthetic anti-ferrimagnetic (SyF)coupling layer 110 is formed here over the first pinning layer 108 bysputtering. The SyF coupling layer 110 can be formed of ruthenium (Ru),rhodium (Rh), Cr, or iridium (Ir) sputtered from a target thereof. Asecond pinning layer 112 is formed over the SyF coupling layer 110 bysputtering. The second pinning layer 112 is formed here of a singlecobalt (Co) layer. The SyF coupling layer 110 is located between thefirst pinning layer 108 and the second pinning layer 112 and causessurface atoms of the first pinning layer 108 and the second pinninglayer 112, when exposed to a magnetic field, to align with surface atomsof the SyF coupling layer 110, thereby pinning the orientation of themagnetic moment of each of the first pinning layer 108 and the secondpinning layer 112. The first pinning layer 108 and the second pinninglayer 112 each include similar magnetic moments, and will thus reactsimilarly when an external magnetic field is applied to the conventionalMTJ stack 100A. The SyF coupling layer 110 maintains an anti-parallelalignment of the magnetic moments of the first 108 and second 112pinning layers.

A structure blocking layer 114 is formed over the second pinning layer112, and here includes tantalum (Ta), molybdenum (Mo), tungsten (W), orcombinations thereof. The structure blocking layer 114 is employedbecause of its crystalline structure, which differs from the crystallinestructure of the first 108 and second 112 pinning layers. The structureblocking layer 114 prevents against formation of a short circuit betweenthe conventional MTJ stack 100A and metallic contacts that can becoupled to the conventional MTJ stack 100A to form MRAM memory cells.

Further in the conventional MTJ stack 100A, a magnetic reference layer116 is formed over the structure blocking layer 114 by sputtering in aPVD chamber. A tunnel barrier layer 118 is formed over the magneticreference layer 116 and a magnetic storage layer 120 is formed over thetunnel barrier layer 118. Each of the tunnel barrier layer 118, themagnetic reference layer 116, and the magnetic storage layer 120 areformed by sputtering a target using an Ar plasma in one or more PVDchambers. The magnetic reference layer 116 and the magnetic storagelayer 120 each include a Co_(x)Fe_(y)B_(z), alloy which may vary incomposition. Additionally, the magnetic storage layer 120 can includeone or more layers of Ta, Mo, W, or Hf, or combinations thereof. Thetunnel barrier layer 118 includes an insulating material, and can befabricated from a dielectric material such as MgO. A composition and athickness of the tunnel barrier layer 118 are selected so as to create alarge tunnel magnetoresistance ratio (TMR) in the tunnel barrier layer118 of the conventional MTJ stack 100A. The TMR is a measurement of achange in resistance in the conventional MTJ stack 100A from theanti-parallel state (R_(ap)) to the parallel state (R_(p)) and can beexpressed as a percentage using the formula ((R_(ap)−R_(p))/R_(p)). Whena bias is applied to the conventional MTJ stack 100A, the tunnel barrierlayer 118 is traversed by spin-polarized electrons, this transmission ofelectrons through the tunnel barrier layer 118 results in electricalconduction between the magnetic reference layer 116 and the magneticstorage layer 120.

A capping layer 122 is formed, by sputtering in a PVD chamber, on themagnetic storage layer 120 and here includes a plurality of interlayers.The capping layer 122 includes a first capping interlayer 122Afabricated from a dielectric material such as MgO. A second cappinginterlayer 122B including a metallic material such as Ru, Ir, Ta, orcombinations thereof, is formed over the first capping interlayer 122A.The first capping interlayer 122A acts as an etch stop layer for hardmask etching and protects the MTJ stack 100A from corrosion. The secondcapping interlayer 122B is configured to electrically communicate withtransistors or contacts when the conventional MTJ stack 100A is laterpatterned, as discussed below with respect to FIG. 1B. A hardmask layer124 is formed in a PVD chamber by sputtering. The hardmask layer 124 isformed over the second capping interlayer 122B to protect theconventional MTJ stack 100A and can be patterned during subsequentoperations.

FIG. 1B is a flow diagram of a method 100B of fabricating memory devicesthat include an MTJ stack 100A and the MTJ stacks fabricated accordingto embodiments of the present disclosure and shown in FIGS. 2A-2F. Themethod 100B is executed in part a plurality of PVD chambers of a PVDsystem that are configured to deposit thin film layers by sputtering.The substrate 102 can be moved among and between sputtering chambers viathe central robotic transfer chamber of the PVD system to form variousthin film layers, including the MTJ stack 100A in FIG. 1A and the MTJstacks shown and discussed below that are fabricated according toembodiments of the present disclosure. In another example, as discussedabove, a plurality of sputtering targets is disposed in a PVD chamberand a shield inside the PVD chamber is configured to selectively protectthe plurality of sputtering targets from plasma exposure or expose atarget thereto. The shield is rotated at different operations of themethod 1006 to expose one or more targets, in series or simultaneously,to the plasma in the PVD chamber.

The layers of FIG. 1A are thus referenced herein with respect to themethod 100B. The operations of the method 100B are performed using oneor more gases including argon (Ar), helium (He), krypton (Kr), xenon(Xe), oxygen (O₂), or nitrogen (N₂) as a plasma species in the PVDchamber or chambers. The processing pressure in the PVD chambers duringthe method 100B can be from about 2 mTorr to about 3 mTorr. Dependingupon the embodiment, the substrate support pedestal (or other structureon which the substrate can be disposed) in the PVD platform is held atfrom −200° C. to 600° C. during fabrication of the pinning and seedlayers of the MTJ stack.

The substrate 102 can be moved among and between PVD chambers dependingupon the composition of the sputtering target(s) used for each layer ofthe MTJ stack 100A, or, as discussed herein, a plurality of targets iscoupled to a power supply and a shield is configured to selectivelyprotect some of the targets, such that one or more targets are exposedin series or simultaneously to form the desired film composition, orboth methodologies can be performed. During sputtering in the PVDchamber, when Ar is used as the sputtering gas, the Ar ions of theplasma bombard the one or more exposed sputtering targets, causingsurface atoms of the sputtering targets to be ejected and deposit as athin film on the substrate. In the method 1006, at operation 128A, asubstrate such as the substrate 102 in FIG. 1A undergoes operationsincluding degassing and pre-cleaning in an Ar gas plasma or in a He/Hplasma. During the method 1006, the substrate is moved between processchambers through or via a central robotic substrate transfer chamber. Atoperation 128B, the substrate 102 is transferred from the centralrobotic substrate transfer chamber to a PVD chamber of a plurality ofPVD chambers. Subsequently, at operation 130, the buffer layer 104 isdeposited on the substrate 102 by sputtering in the target of the PVDchamber. A power from 1 kW to 100 kW is applied to the one or more PVDchambers discussed herein to ionize a portion of the Ar and form theplasma used in operation 130. The ejected surface atoms of the targetare deposited on the substrate 102 to form the buffer layer 104.

During formation of the buffer layer 104 at operation 130, a sputteringtarget or targets including Co_(x)Fe_(y)B_(z), TaN, and/or Ta aresputtered in the PVD chamber using Ar plasma to form the buffer layer104. In an embodiment where the buffer layer 104 is or includes Ta, thebuffer layer 104 is sputtered in a PVD chamber using a Ta target and Arplasma. In an example where the buffer layer 104 is or includes TaN,operation 130 is performed when nitrogen gas (N₂) is present in the PVDchamber and Ar plasma is used to sputter a Ta sputtering target to formthe TaN buffer layer 104. In another example where the buffer layer 104is or includes TaN, operation 130 is performed in a PVD chamber using aTaN sputtering target and Ar plasma to form the buffer layer 104. Duringformation of the buffer layer 104 and subsequent layers, the one or morePVD chambers used are maintained at vacuum pressure.

Subsequently, in operation 132, the seed layer 106 is deposited on thebuffer layer 104 by sputtering a target in a PVD chamber. In anembodiment of operation 132, the seed layer 106 is formed in the samePVD chamber as the PVD chamber that was used to form the buffer layer104, using a different sputtering target than the sputtering target usedto deposit the buffer layer 104. The first pinning layer 108 isdeposited on the seed layer 106 at operation 134 by sputtering a targetin a PVD chamber. The first pinning layer 108 is shown as an example inthe conventional MTJ stack 100A, and can be formed at operation 134 in aPVD chamber by sputtering one or more targets using Ar plasma. In anexample where the first pinning layer 108 is Co layer, a Co targetsputtered using Ar plasma in the PVD chamber. In an example where thefirst pinning layer 108 includes one or more bilayers, operation 134uses a Co sputtering target to form the first interlayer of the bilayerand uses another sputtering target composed of a different element toform the second interlayer of the bilayer. Depending upon theembodiment, the Co sputtering target and the sputtering target of theother element can be sputtered using Ar plasma in the same PVD chamberor each layer of the bilayer can be formed in separate PVD chambers.

In an example according to embodiments of the present disclosure, whichcan be combined with other examples herein, a first pinning layer 208 asshown in FIGS. 2A and FIG. 2C is formed using a PVD chamber at operation134. In this example, the first pinning layer 208 is formed in the PVDchamber at operation 134 using one or more sputtering targets. Todeposit the first pinning layer 208, xenon (Xe) or argon (Ar) gas isintroduced to the PVD chamber at a flow rate of about 2 sccm-40 sccm.The Xe or Ar gas is introduced to the PVD chamber while a power from 50W to 10000 W is applied to the target at a negative voltage to form aplasma. In another example, the Xe or Ar gas is introduced to the PVDchamber at a flow rate from 5 sccm to 20 sccm, and, in some examples, ata flow rate of 10 sccm. In another example, the power applied to the oneor more sputtering targets used to form the first pinning layer 208 isfrom 100 W to 800 W, and, another example, the power applied to the oneor more sputtering targets can be 400 W.

Depending upon a composition of the first pinning layer 208, Xe gas canbe used in the sputtering operation in the PVD chamber at operation 134to form the plasma since it is a heavier gas than Ar, and thereforeyields ions with higher atomic weights than the ions formed using Ar orother, lighter, gases. Thus, the Xe plasma bombards the target with moreenergy than the Ar plasma and can be used to sputter deposit layers suchas Pt. In one example of the first pinning layer 208 in the presentdisclosure, Xe, Ar or a mixture thereof is introduced into the PVDchamber at a flow rate from about 10 sccm and a power of 400 W isapplied to the target at a negative voltage to form Ar or Xe plasma. Inone example, the first pinning layer 208 is fabricated from alattice-matching layer of Pd or Pt by sputtering a Pd target or a Pttarget. The lattice-matching layer of the first pinning layer 208 isfrom about 1 Å to about 3 Å thick.

In another example, the first pinning layer 208 includes at least onebilayer that includes two interlayers, and the lattice-matching layerincluding Pt or Pd is formed over the at least one bilayer, as shown inFIG. 2C. In an example where at least one bilayer is used to form thefirst pinning layer 208 in addition to the lattice-matching layer, thebilayer includes a first interlayer of Co and a second interlayer ofanother element such as Pt, Pd, or Ni, or combinations or alloysthereof. The bilayer of the first pinning layer 208 can be formed atoperation 134 in a PVD chamber which includes a plurality of targetsincluding the Co target and a target formed from Pt, Pd, or Ni, orcombinations or alloys thereof, or in separate PVD chambers, one PVDchamber containing a Co target and the other PVD chamber containing atarget of Pt, Pd, or Ni, or combinations or alloys thereof. In oneexample, the plurality of sputtering targets is disposed in a single PVDchamber and sputtered using Ar plasma and/or Xe plasma. Each of the Cotarget and the target of the other element can be selectively exposed tothe plasma using the shield discussed herein. The selective targetexposure forms the Co interlayer of the bilayer and to form aninterlayer of the other element to form a resultant bilayer. Theinterlayer depositions can be repeated at operation 134 for a pluralityof iterations to form one or more bilayers of the first pinning layer208, as shown in FIG. 2C.

The SyF coupling layer 110 is deposited on the first pinning layer 108at operation 136 by sputtering a target of Ru, Cr, Rh, or Ir in a PVDchamber using Ar, Kr, or Xe plasma. In one example of an SyF couplinglayer 210 according to embodiments of the present disclosure as shown inFIG. 2A, the SyF coupling layer 210 is deposited in a PVD chamber atoperation 136 using a sputtering target of Ru, Cr, Rh, or Ir. In oneexample of forming the SyF coupling layer 210 at operation 136, an Irsputtering target is sputtered in the PVD chamber using Kr or Xe as theplasma gas. The Xe gas or Kr gas, from which the plasma is formed, isintroduced into the PVD chamber at a flow rate from 10 sccm to 25 sccm,and in some examples, at a gas flow rate of 16 sccm. In another exampleof forming the SyF coupling layer 210 at operation 136, a Ru sputteringtarget is sputtered in the PVD chamber using Ar plasma. The Ar gas usedto form plasma to sputter the Ru target is introduced to the PVD chamberat a gas flow rate which can be, for example, from 2 sccm to 10 sccm,and, in some examples, the Ar gas flow rate is 6 sccm. Further in theexample at operation 136, when either Kr, Xe, or Ar gas is used in thePVD chamber, a power from between 150 W and 300 W is applied to thetarget at a negative voltage to form and maintain the Kr, Xe, or Arplasma. In other example, a power of about 250 W is applied to thetarget. The SyF coupling layer 210 is deposited at operation 136 incontact with a lattice-matching layer of the first pinning layer 208.

The second pinning layer 112 is deposited on the SyF coupling layer 110in a PVD chamber at operation 138. In one example, the second pinninglayer 112 is formed of Co using a Co target and Ar plasma in the PVDchamber. In another example, the second pinning layer 112 includes abilayer, and may or may not include a Co layer formed in contact withthe bilayer. In this example, the second pinning layer 112 is formed ina PVD chamber using a Co sputtering target and a second metal sputteringtarget, and a shield is adjusted to expose each of the Co and secondmetal sputtering targets separately, in at least one iteration, to formone or more bilayers of the second pinning layer 112. In other examples,each layer of the bilayer of the second pinning layer 112 can be formedin a different PVD chamber, where one PVD chamber includes a Cosputtering target and the other PVD chamber includes a sputtering targetof the second metal.

In one example of a second pinning layer 212 according to embodiments ofthe present disclosure as shown in FIGS. 2A and 2D, the second pinninglayer 212 is deposited in a PVD chamber at operation 138 using Ar plasmaand/or Xe plasma, depending upon the target material being sputtered. Inan embodiment of the present disclosure, the second pinning layer 212 isfabricated at operation 138 of a lattice-matching layer of Pt that isdeposited on the SyF coupling layer 210 by sputtering a Pt target withXe plasma. In an embodiment, the second pinning layer 212 furtherincludes a bilayer that includes a first interlayer of Co and a secondinterlayer of Pt, Ni, or Pd. The bilayer is formed on thelattice-matching layer of the second pinning layer 212.

In an example where at least one bilayers is formed as a part of thesecond pinning layer, the bilayer is formed in a PVD chamber using a Cosputtering target to form the first interlayer of the bilayer and asecond metal sputtering target to form the second interlayer of thebilayer. The second sputtering target can be formed from Pt, Pd, or Ni.In another example, the second sputtering target can be formed from analloy including one or more of Pt, Pd, or Ni, and a shield is adjustedto expose each of the Co and second metal sputtering targets separately,in at least one iteration, to form one or more bilayers of the secondpinning layer 212. Xenon can be used to deposit the second pinning layer212 when metals such as Pt are used to form the second pinning layer 212since Xe is a heavier gas than Ar gas and can thus interact with heaviermetals including Pt more effectively during sputtering processes in aPVD chamber. In an embodiment, the second pinning layer 212 furtherincludes a Co layer formed over the at least one bilayer. The Co layerformed over the at least one bilayer can have a thickness of up to 10 Å.In an embodiment, the second pinning layer 212 can have a totalthickness from 0.3 nm to 15 nm. In an embodiment where Xe gas is used toform plasma in the PVD chamber, the Xe gas is introduced into the PVDchamber at a flow rate from about 2 sccm to about 40 sccm, or from 5sccm to 20 sccm, and, in some embodiments, the Xe gas is introduced intothe PVD chamber at a flow rate of about 10 sccm. During the formation ofthe second pinning layer 212, a power from 50 W to about 1000 W isapplied to the target at a negative voltage to form and maintain the Arand/or Xe plasma. In some examples, a power from 100 W to 600 W isapplied to the target at a negative voltage to form and maintain the Arand/or Xe plasma, and, in some embodiments a power of about 200 W isapplied to the target at a negative voltage.

The structure blocking layer 114 is formed at operation 140 in a PVDchamber that includes sputtering targets including Ta, Mo, and/or W,depending upon an intended composition of the structure blocking layer114. When two or more sputtering targets of Ta, Mo, and W are used, eachtarget may be used in a separate PVD chamber, or the two or moresputtering targets can be sputtered sequentially or simultaneously inthe PVD chamber using the shield adjustment discussed above, dependingupon the intended composition of the structure blocking layer 114. Themagnetic reference layer 116 is subsequently deposited on the structureblocking layer 114 at operation 142, and can be formed in a PVD chamberwhere other layers of the MTJ stack 100A may also be formed. This maydepend, for example, upon the composition of other layers such as thebuffer layer 104, if both the buffer layer 104 and magnetic referencelayer 116 are Co_(x)Fe_(y)B_(z)-based. The magnetic reference layer 116can be formed in a PVD chamber using a sputtering target that is aCo_(x)Fe_(y)B_(z) alloy. In other examples, the magnetic reference layer116 can be deposited using individual sputtering targets of Co, Fe, orB, or by a combination of an alloy sputtering target and asingle-element sputtering target, e.g., a CoFe target and a B target.

The tunnel barrier layer 118 is deposited on the magnetic referencelayer 116 at operation 144. In one example of operation 144, the tunnelbarrier layer 118 is formed in a PVD chamber using a metal-oxide targetsuch as MgO and Ar gas based plasma. In an alternate embodiment, thetunnel barrier layer 118 is formed in the PVD chamber at operation 144using a metal target such as Mg, Ti, Hf, Ta, or Al and Ar gas basedplasma while O₂ is present in the PVD chamber to form the metal-oxide ofthe tunnel barrier layer 118. At operation 146, the magnetic storagelayer 120 is formed in a PVD chamber. The formation of the magneticstorage layer 120 can occur in various ways depending upon the intendedcomposition. The magnetic storage layer 120 can include one or morelayers of Co_(x)Fe_(y)B_(z), and, in some examples, one or more layersof Ta, Mo, W, or Hf. As such, the deposition of the magnetic storagelayer 120 in the PVD chamber can include Ar plasma and aCo_(x)Fe_(y)B_(z) alloy target, or individual targets of Co, Fe, and B,or a combination of an alloy target and an element target such as a CoFetarget and a B target. In examples where the magnetic storage layer 120includes Ta, Mo, W, or Hf, a sputtering target of Ta, Mo, W, or Hf issputtered in the chamber using plasma formed from Ar.

In one example, the magnetic storage layer 120 can be formed in a singlePVD chamber using an Ar plasma. The magnetic storage layer 120 can bedeposited by adjusting a shield to expose or protect one or more targetssuch as those discussed above that are used to form Co_(x)Fe_(y)B_(z)and layers of Ta, Mo, W, or Hf. In another example, a Co_(x)Fe_(y)B_(z)layer of the magnetic storage layer 120 is sputtered in a PVD chamberusing a Co_(x)Fe_(y)B_(z) alloy target using Ar plasma. In anotherexample, the Co_(x)Fe_(y)B_(z) layer is formed in the PVD chamber byusing individual Co, Fe, and B, targets and Ar gas based plasma. Instill another example, the Co_(x)Fe_(y)B_(z) layer is formed in the PVDchamber using an Ar gas based plasma and an alloy target and a compoundelement target, for example, a CoFe target and a B target. The Ta, Mo,W, or Hf layer of the magnetic storage layer 120 can be sputtered in thePVD chamber using a Ta target, a Mo target, a W target, or a Hf target.

At operation 148, the capping layer 122 is deposited on the magneticstorage layer 120. In an embodiment, the first capping interlayer 122Aof the capping layer 222 is formed in a PVD chamber that may bedifferent than the PVD chamber where non-oxide layers are formed, asboth Ar plasma and O₂ are present in the PVD chamber during operation148 when oxide layers are formed. The first capping interlayer 122A isdeposited in the PVD chamber by sputtering a Mg target using an Arplasma, O₂ is also present in the PVD chamber. In another example atoperation 148, the first capping interlayer 122A is formed in the PVDchamber using an MgO sputtering target and Ar plasma. In an examplewhere the first capping interlayer 122A is to be formed of the samematerial (e.g., Mg) as the tunnel barrier layer 118, the PVD chamberused for operation 144 can be the same PVD chamber that is used foroperation 148 to form the first capping interlayer 122A. The secondcapping interlayer 122B is deposited on the first capping interlayer122A at operation 150. If O₂ is used in operation 148, operation 150 canoccur in a separate, different, PVD chamber than that used to sputterthe first capping interlayer 122A, since there is no O₂ used in the PVDchamber to form the first capping interlayer 122A. The second cappinginterlayer 122B is formed in a PVD chamber using Ar plasma and one ormore sputtering targets composed of Ru, Ir, and/or Ta. Depending uponthe composition of the second capping interlayer 122B, operation 150 mayoccur in a PVD chamber that is also used to form, for example, the SyFcoupling layer 110 at operation 136.

Further in the method 1006, at operation 152, a hardmask layer 124 isdeposited over the second capping interlayer 122B in a PVD chamber.Depending upon the type of hardmask layer 124 used in the MTJ stack100A, operation 152 may or may not occur in the presence of O₂. Forexample, if the hardmask layer 124 is a metal-oxide hardmask, an O₂ andAr based plasma can be used during operation 152 along with a metallicsputtering target or targets to form the metal-oxide layer, or ametal-oxide sputtering target can be used to deposit the hardmask layer124, in which case O₂ is not used in hardmask layer 124 formation atoperation 150. In some embodiments, when the hardmask layer 124 isamorphous carbon or spin-on carbon, operation 152 occurs in a CVD orspin-on deposition chamber.

Further in the method 1006, the MTJ stack 100A (or MTJ stack 200 shownbelow in FIG. 2A) formed at operations 128A-152 can be subjected to oneor more processes that are collectively indicated by operation 154 inthe method 1006. These operations can include high-temperature (on theorder of 400° C.) operations. In one example, the processes at operation154 may include a pre-patterning anneal operation, which is followed byan MTJ patterning operation. In an alternate embodiment, the MTJpatterning at operation 154 can include a plurality of processes such aspatterning the hardmask layer 124 and can further include an operationto etch the MTJ stack 100A after the hardmask layer 124 is patterned toform a plurality of individual pillars from the MTJ stack 100A using thepatterned hardmask layer as an etch mask.

In an alternate embodiment at operation 154, a thermal annealingoperation is executed to repair, crystallize, and enhance latticestructures of the film stack, including the magnetic storage layer(s)and the magnetic reference layer(s) in the MTJ stack 100A. The thermalannealing performed at operation 154 can act to further crystallize atleast the material of the magnetic reference layer(s) 116 and magneticstorage layer(s) 120. The crystallization of the magnetic referencelayer(s) and magnetic storage layer(s) upon deposition of those layersestablishes the perpendicular anisotropy of the MTJ stack 100A, whilemaintaining its desired electrical and mechanical properties.Embodiments of MTJ stacks fabricated following the operations of themethod 1006 are shown and discussed below, and the embodiments areconfigured to maintain the as-deposited face-centered cubic (fcc) <111>crystalline structure of the pinning layers after the thermal annealingoperation executed at operation 154, and/or during additional oralternate back end processing operations that occur at high temperatureson the order of 400° C. The MTJ stacks fabricated according toembodiments of the present disclosure include a SyF coupling layer inbetween a first pinning layer and a second pinning layer. In anembodiment, the first pinning layer includes a first lattice-matchinglayer and the second pinning layer includes a second lattice-matchinglayer, each of the first lattice-matching layer and the secondlattice-matching layer is formed of platinum (Pt) or palladium (Pd). Thefirst lattice-matching layer of the first pinning layer and the secondlattice-matching layer of the second pinning layer are referred to assuch herein at least in part because the materials from which each ofthe first and the second lattice matching layers are fabricated areselected to have a lattice constant within about +/−4% of the materialfrom which the SyF coupling layer is fabricated. The SyF coupling layeris in contact with each of the first lattice-matching layer of the firstpinning layer and the second lattice-matching layer of the secondpinning layer. This is in contrast to other MTJ stacks where the SyFcoupling layer is in contact with a Co layer of the first pinning layerand a Co layer of the second pinning layer

In an embodiment, each of the first pinning layer and/or the secondpinning layer further include at least one bilayer formed in contactwith the respective lattice-matching layer. In one example, each of thefirst lattice-matching layer from the first pinning layer and the secondlattice-matching layer from the second pinning layer are in contact withthe SyF coupling layer, and the SyF coupling layer is formed from Ir.Each bilayer includes a first interlayer and a second interlayer. In oneexample of the first pinning layer, the first pinning layer includes thefirst lattice-matching layer and a bilayer including a first interlayerof Co and a second interlayer of Ni. In another example of the firstpinning layer, the first pinning layer includes the firstlattice-matching layer and the at least one bilayer includes a firstinterlayer of Co and a second interlayer of Pt. In another example ofthe first pinning layer, the first pinning layer includes the firstlattice-matching layer and the at least one bilayer includes a firstinterlayer of Co and a second interlayer of Pd. In an example of thesecond pinning layer, the second pinning layer includes the secondlattice-matching layer and a bilayer including a first interlayer of Coand a second interlayer of Pt. In another example, the second pinninglayer includes the second lattice-matching layer and a bilayer includinga first interlayer of Co and a second interlayer of Pd. In anotherexample, the second pinning layer includes the second lattice-matchinglayer and a bilayer that includes a first interlayer of Co and a secondinterlayer of Ni. The second lattice-matching layer is in contact withthe SyF coupling layer, which includes Ir. Further in an example of thesecond pinning layer, a Co layer is formed over the one or more bilayersand is in contact with the structure blocking layer.

Depending upon the embodiment, the first pinning layer and the secondpinning layer can each include the same layer structure, materials,and/or thickness, or can vary in layer structure, materials, and/orthickness. Using the MTJ stacks discussed herein, there is an improvedlattice matching between the first pinning layer and the SyF couplinglayer, and between the SyF coupling layer and the second pinning layer.The improved lattice matching reduces the effect of a dipole field onthe magnetic storage layer as discussed below. Lattice matching asdiscussed herein includes fabricating layers including the first pinninglayer, the second pinning layer, and the SyF coupling layer such that adifference in the lattice constants, referred to herein as the latticemismatch, between the first pinning layer and the SyF coupling layer isreduced, as is the lattice mismatch between the second pinning layer andthe SyF coupling layer. The lattice mismatch is defined in equation (1):

LM=[(a ₁ −a ₂)/a ₁]×100   (1)

In equation (1), a₁ is a lattice constant of a first material and a₂ isa lattice constant of a second material. In embodiments of the presentdisclosure, the lattice mismatch between the SyF coupling layer of theMTJ stack and the first pinning layer is less than about +/−4%, and thelattice mismatch between the SyF coupling layer and the second pinninglayer is less than +/−4%.

Further in the MTJ stacks discussed herein, when each of the firstpinning layer and the second pinning layer includes at least onebilayer, a ratio of the thickness of the interlayers of each bilayer ofthe first pinning layer and the second pinning layer can be adjusted soas to reduce a dipole field effect on the stack when a magnetic field isapplied. The thickness ratios discussed herein can be calculated foreach bilayer in a pinning layer, if more than one bilayer is used. Inother examples, a thickness ratio can be calculated as an average acrossbilayers, such that the thickness ratio for a pinning layer iscalculated using an average of the first interlayer thickness and anaverage of the second interlayer thickness across the bilayers of thepinning layer. The thickness ratio is discussed in detail below, and isa calculation of a thickness of a first interlayer of a bilayer of apinning layer and a thickness of a second interlayer of the bilayer of apinning layer. Using the MTJ stacks discussed herein, the crystalstructures of the SyF coupling layer and the magnetic coupling of themagnetic reference layer and the magnetic storage layer aresubstantially maintained in the same as-deposited state, even afterannealing. For example, the MTJ stacks discussed herein can be for aperiod of from 0.5 hours to at least 3 hours at about 400° C., and themagnetic and electric properties of the MTJ stacks are thus maintained.

FIG. 2A is a schematic illustration of an MTJ stack 200 according to anembodiment of the present disclosure. In the illustrated embodiment, abuffer layer 204 is formed via sputtering in a PVD chamber on aconductive portion of a substrate 202, or on a conductive film layer onthe substrate 202. The substrate 202 can include one or more of tungsten(W), tantalum nitride (TaN), titanium nitride (Tin), or other metallayers. The buffer layer 204 improves the adhesion of a seed layer 206to the substrate 202. The improved adhesion of the seed layer 206 to thesubstrate 202 aids in the formation and performance ofsubsequently-deposited layers of the MTJ stack 200. The buffer layer 204includes Co_(x)Fe_(y)B_(z), Ta, and/or TaN, and is formed in one or morePVD deposition operations in a PVD chamber using Ar plasma. In oneexample, the buffer layer 104 is formed in a PVD chamber using Ar plasmaand a sputtering target that is a Co_(x)Fe_(y)B_(z) alloy. In anotherexample, the buffer layer 104 is formed using individual sputteringtargets of Co, Fe, or B. In another example, the buffer layer 104 isformed by using a combination of an alloy sputtering target and asingle-element sputtering target, e.g., a CoFe target and a B target. Inan example where a Ta layer is included in the buffer layer 204, the Talayer can be formed in a PVD chamber using a Ta target and Ar plasma.

In one example, the buffer layer 204 includes TaN and it is sputteredonto the substrate 202 in the PVD chamber using a Ta target, Ar plasma,and N₂. The N₂ reacts with the Ta material sputtered from the Ta targetto form the TaN layer. In another example, a TaN sputtering target isused in the PVD chamber with Ar plasma to form the buffer layer 204. Inone example, the buffer layer 204 is sputtered directly on and incontact with a conductive layer on the substrate 202. In other examples,there is a conductive transitional layer in between the conductive layeron the substrate 202 and the buffer layer 204 that does not affectperformance of the MTJ stack. The buffer layer 204 is optionallyemployed in the illustrated embodiment, and may not be used in someembodiments discussed herein. When a buffer layer 204 is employed, anoverall thickness of the buffer layer 204 is from 0 Å (no buffer layerused) to about 60 Å. In one example, the buffer layer 204 is a singlelayer of Ta, TaN, or Co_(x)Fe_(y)B_(z) sputtered directly on, and incontact with, a conductive layer on the substrate 202 to a thickness ofup to 10 Å. In another example, the buffer layer 204 is a combination oftwo or more layers, and each layer of the buffer layer 204 is Ta, TaN,or Co_(x)Fe_(y)B_(z) In this example, each layer of the buffer layer 204can be from 1 Å to 60 Å thick. In an example where the buffer layer 204is formed from TaN instead of Ta or Co_(x)Fe_(y)B_(z), the buffer layer204 can be up to 20 Å thick. In another example, which can be combinedwith other examples herein, where Co_(x)Fe_(y)B_(z) is employed alone toform the buffer layer 204. In this example, the buffer layer 204 canhave a thickness of about 10 Å. In another example at least one of Ta orTaN is employed in conjunction with Co_(x)Fe_(y)B_(z), to form thebuffer layer 204. In this example, an average thickness of the bufferlayer 204 is about 20 Å.

The seed layer 206 is deposited in a PVD chamber via sputtering one ormore targets. The seed layer 206 is deposited on the buffer layer 204.The seed layer 206 includes Cr or Pt. The formation of the seed layer206 in the PVD chamber is discussed in detail above at operation 132. Inan embodiment, the seed layer 206 is 100 Å or less in thickness. In oneexample, which can be combined with other examples herein, the seedlayer 206 is from about 30 Å to about 60 Å thick. In one example, theseed layer 206 is formed directly on and in contact with the bufferlayer 204. In other examples, there is a transitional layer in betweenthe seed layer 206 and the buffer layer 204 that does not affectperformance of the MTJ stack.

Further in the MTJ stack 200, a first pinning layer 208 is formed on theseed layer 206 in a PVD chamber. The formation of the first pinninglayer 208 is shown in detail above at operation 134 of the method 100Bin FIG. 1B, and occurs in a PVD chamber using Ar or Xe plasma and one ormore sputtering targets. In one example, the first pinning layer 208 isfabricated as one or more bilayers of various materials and alattice-matching layer formed over the one or more bilayers, such thatthe lattice-matching layer of the first pinning layer is in contact withthe SyF coupling layer 210, as shown in FIG. 2C. The lattice-matchinglayer of the first pinning layer 208 can be formed from Pt or Pd. Thefirst pinning layer 208 is deposited over the one or more bilayers usingXe plasma using a Pt or Pd sputtering target. In an example where one ormore bilayers are included in the first pinning layer 208, each bilayercontains a first interlayer of Co and a second interlayer of anotherelement or alloy. The at least one bilayer of the first pinning layer208 is formed by sputtering a Co target using Ar plasma and,subsequently, sputtering a second target of Pt, Ni, or Pd, orcombinations or alloys thereof, using the Ar or Xe plasma. In an examplewhere a Pt is target sputtered in addition to a Co target to form thebilayer of the first pinning layer 208, Xe plasma may be used instead ofor in addition to Ar plasma. In an embodiment where one or more bilayersare used to form the first pinning layer, repeated deposition cycles inthe PVD chamber can be performed by forming a first interlayer of abilayer, where the first interlayer includes Co. The first interlayer ofthe bilayer can be formed by shielding targets that do not include Co,and, subsequently, by shielding the Co target and other targets toexpose a second target that includes a second element to be used todeposit the second interlayer of the bilayer. The deposition of thefirst interlayer and the second interlayer may be repeated in aniterative fashion to form one or more bilayers of the first pinninglayer 208. In one example, the first pinning layer 208 is formed in thePVD chamber directly on and in contact with the seed layer 206. In otherexamples, there is a transitional layer in between the seed layer 206and the first pinning layer 208 that does not affect performance of theMTJ stack.

A synthetic anti-ferrimagnetic (SyF) coupling layer 210 is deposited ina PVD chamber on the first pinning layer 208, and a second pinning layer212 is sputter deposited on the SyF coupling layer 210. The SyF couplinglayer 210 is formed in the PVD chamber using Kr or Xe plasma with a Rusputtering target, an Rh sputtering target, a Cr sputtering target, oran Ir sputtering target. The SyF coupling layer 210 has a thickness fromabout 3 Å to about 10 Å. In an embodiment, the second pinning layer 212is fabricated by sputtering a Pt target or a Pd target in a PVD chamberusing an Ar or Xe plasma to form a lattice-matching layer of the secondpinning layer 212 on the SyF coupling layer 210. In some examples, thesecond pinning layer 212 includes at least one bilayer formed over thelattice-matching layer. The at least one bilayer of the second pinninglayer 212 includes a first interlayer of Co and a second interlayer ofNi, Pd, or Pt, or combinations or alloys thereof. In one example, theSyF coupling layer 210 is formed directly on and in contact with thelattice-matching layer of first pinning layer 208 and thelattice-matching layer of the second pinning layer 212. In otherexamples, there is a transitional layer in between the SyF couplinglayer 210 and either or both of the first pinning layer 208 or secondpinning layer 212 that does not affect performance of the MTJ stack.

The formation of the second pinning layer 212 is discussed at operation138 of the method 100B in FIG. 1B above. The second pinning layer 212includes a lattice-matching layer of Pt or Pd formed on the SyF couplinglayer 210, as well as one or more bilayers formed over thelattice-matching layer. The lattice-matching layer of the second pinninglayer 212 can be formed to a thickness up to 3 Å by sputtering a Pttarget or a Pd target using Xe plasma. In an example where one or morebilayers are included in the second pinning layer 212, a first bilayeris formed on the lattice-matching layer and includes a first interlayerof Co and a second interlayer of another element such as Pd, Ni, or Pt,or combinations or alloys thereof. The bilayer is formed by sputtering aCo target using an Ar plasma and, subsequently, by sputtering a secondtarget of Pt, Ni, or Pd, or combinations or alloys thereof, using Xe orAr plasma. In an embodiment, repeated deposition cycles of the firstinterlayer and the second interlayer in a PVD chamber using the Cotarget and the second target can be used to form the one or morebilayers of the second pinning layer 212. A thickness of each bilayer ofthe second pinning layer 212 can be from about 4 Å to about 15 Å. In anexample, the thickness of the second pinning layer 212 is from about 0.3nm to 15 nm. Alternate configurations of the second pinning layer 212are shown in FIG. 2D.

In an embodiment where the first pinning layer 208 and the secondpinning layer 212 each include one or more bilayers, a thickness ratiocan be defined for each pinning layer. The thickness ratios discussedherein are a ratio of a thickness of the interlayers of the one or morebilayers of each pinning layer. A thickness ratio as discussed hereincan be expressed as (X:Y), where X is a thickness of the firstinterlayer that includes Co, Y is a thickness of the second interlayerof Pt, Ni, or Pd, or an alloy of Pt, Ni, and/or Pd, and z indicates thelayer associated with the thickness ratio, for example, whether thethickness ratio is for the first pinning layer 208 or the second pinninglayer 212. In one example, the first interlayer of the first pinninglayer 208 is from 1 Å to 8 Å thick and the second interlayer of thefirst pinning layer 208 is from 1 Å to 8 Å thick. In another example,the first interlayer of the second pinning layer 212 is from 1 Å to 8 Åthick and the second interlayer of the second pinning layer 212 is from1 Å to 8 Å thick. In this example, a thickness ratio of the firstpinning layer 208 [(Co:Y)₂₀₈] is greater than a second pinning layer 212thickness ratio [(Co:Y)₂₁₂].

Subsequent to fabrication of the MTJ stack 200, operations includingetching the MTJ stack 200 can be performed as part of MRAM devicefabrication. After etching, when a magnetic field is applied to the MRAMdevice, a magnetic dipole field is generated from the first pinninglayer 208 to a magnetic storage layer 220 (discussed below). The dipolefield can negatively impact the performance of layers of the MTJ stack200, including the magnetic storage layer 220. Since the second pinninglayer 212 is closer to the magnetic storage layer 220 than the firstpinning layer 208 in the MTJ stack 200, a thickness ratio of the firstpinning layer 208 is greater than the thickness ratio of the secondpinning layer 212, which minimizes dipole field experienced by themagnetic storage layer 220. Accordingly, by increasing the magneticmaterial content of the first pinning layer 208 as compared to themagnetic material content of the second pinning layer 212, the dipolefield experienced by the magnetic storage layer 220 is reduced. Themagnetic material content of the first or second pinning layers is anamount of a material such as Co or Ni that is capable of retainingmagnetization in response to the application of a magnetic field. Thisis in contrast to materials such as Pt or Pd which can also be used toform one or more pinning layers. In one example, a thickness ratio ofthe first pinning layer (Co:Y)₂₀₈ can be from 1:1 to 8:1, and athickness ratio of the second pinning layer (Co:Y)₂₁₂ can be from 1:1 to8:8. In this example, an MTJ stack 200 includes the first pinning layer208 with a thickness ratio (Co:Y)₂₀₈ of 8:1, and the second pinninglayer 212 with a thickness ratio (Co:Y)₂₁₂ of 8:8. In another example,an MTJ stack 200 includes the first pinning layer 208 with a thicknessratio (Co:Y)₂₀₈ of 8:3, and the second pinning layer 212 with athickness ratio (Co:Y)₂₁₂ of 3:7. In other examples, the ratios(Co:Y)₂₀₈ and (Co:Y)₂₁₂ can further vary, with [(Co:Y)₂₀₈>(Co:Y)₂₁₂].When Y is a magnetic material such as Ni, the thickness ratios can befurther tailored depending upon the embodiment, and/or a fewer number ofbilayers can be used to form the second pinning layer 212 than thenumber of bilayers that is used to form the first pinning layer 208. Insome examples, the second pinning layer 212 does not include a bilayer.

Further in the MTJ stack 200, a structure blocking layer 214 isoptionally formed on the second pinning layer 212 by sputtering amaterial layer thereon in a PVD chamber. The structure blocking layer214 prevents against formation of a short circuit between the MTJ stack200 and metallic contacts that can be coupled to the MTJ stack 200 toform MRAM memory cells. In one example, during deposition of thestructure blocking layer 214 in the PVD chamber, depending upon theintended composition of the layer, one or more individual Ta, Mo, or Wsputtering targets can be sputtered the PVD chamber using Ar plasma. Inanother example, during deposition of the structure blocking layer 214in the PVD chamber, or one or more alloy targets including alloys of Ta,Mo, and/or W can be sputtered in the PVD chamber using Ar plasma. Thestructure blocking layer 214 is a body-centered-cubic (bcc) structureoriented in the <100> direction, in contrast to the seed layer 206 andthe first pinning layer 208 and the second pinning layer 212 which caneach be oriented in a face-centered-cubic <111> direction. The structureblocking layer 214 is from 0 (no layer) Å to about 8 Å thick, and, inone example, a thickness of 4 Å is sputter deposited. In one example,the structure blocking layer 214 is formed directly on and in contactwith the second pinning layer 212 by sputter deposition. In otherexamples, there is a transitional layer in between the structureblocking layer 214 and the second pinning layer 212 that does not affectperformance of the MTJ stack.

A magnetic reference layer 216 is formed on the structure blocking layer214 by sputter deposition in a PVD chamber using Ar plasma. The magneticreference layer 216 can be deposited in the PVD chamber using a singleCo—Fe—B alloy sputtering target, or by using two or more of a Cosputtering target, an Fe sputtering target, or a B sputtering target. Inanother example, the magnetic reference layer 216 can be formed in thePVD chamber using Ar plasma, an alloy target, and an element target,such as a CoFe target and a B target. The magnetic reference layer 216can be sputtered to a thickness from 1 Å to 15 Å, and, in one example,can be formed to a thickness of 10 Å. The magnetic reference layer 216includes Co_(x)Fe_(y)B_(z) where z is from about 10 wt. % to about 40wt., y is from about 20 wt. % to about 60 wt. %, and x is equal to orless than 70 wt. %. In an embodiment, z is at least 20 wt. %. In oneexample, the magnetic reference layer 216 is formed directly on and incontact with the structure blocking layer 214. In other examples, thereis a transitional layer between the magnetic reference layer 216 and thestructure blocking layer 214 that does not affect performance of the MTJstack.

A tunnel barrier layer 218 is formed on the magnetic reference layer 216using sputtering of a target in a PVD chamber in an Ar plasma. Thetunnel barrier layer 218 includes a metal-oxide such as magnesium oxide(MgO), hafnium oxide (HfO₂), titanium oxide (TiO₂), tantalum oxide(TaO_(x)), aluminum oxide (Al₂O₃), or other materials as appropriate forvarious applications. Thus, the tunnel barrier layer 218 can be formedin the PVD chamber using Ar plasma and a sputtering target of ametal-oxide. Alternately, the tunnel barrier layer 218 can be formed inthe PVD chamber using Ar plasma, O₂, and a sputtering target of themetal of the desired metal-oxide, where the metal-oxide layer is formedwhen the metal layer sputtered from the metal sputtering target isexposed to the O₂. The tunnel barrier layer 218 has a thickness from 1 Åto 15 Å, with a thickness of 10 Å in some embodiments. In one example,tunnel barrier layer 218 is formed directly on and in contact with themagnetic reference layer 216. In other examples, there is a transitionallayer between the tunnel barrier layer 218 and the magnetic referencelayer 216 that does not affect performance of the MTJ stack.

In an embodiment, the MTJ stack 200 further includes a magnetic storagelayer 220 formed on the tunnel barrier layer 218 using a sputteringoperation in a PVD chamber as discussed herein. The magnetic storagelayer 220 can include one or more layers of Co_(x)Fe_(y)B_(z), and, insome examples, one or more layers of Ta, Mo, W, or Hf. As such, thedeposition of the magnetic storage layer 220 in the PVD chamber caninclude using Ar plasma, a Co_(x)Fe_(y)B_(z) alloy target, or individualtargets of Co, Fe, and B, or a combination of an alloy target and anelement target such as a CoFe target and a B target. In examples wherethe magnetic storage layer 220 is formed from one or more of Ta, Mo, W,or Hf, a sputtering target of Ta, Mo, W, or Hf is sputtered in thechamber using a plasma formed of Ar.

The magnetic storage layer 220 is from about 5 Å to about 20 Å inthickness depending upon factors including a material or materials usedto form the magnetic storage layer 220. In one example, the magneticstorage layer is fabricated from Co_(x)Fe_(y)B_(z) where z is from about10 wt. % to about 40 wt. %, y is from about 20 wt. % to about 60 wt. %,and x is equal to or less than 70 wt. %. In this example, the thicknessof the magnetic storage layer 220 is from 5 Å to 40 Å. In anotherexample, the thickness of the magnetic storage layer 220 is about 20 Å.In one example, the magnetic storage layer 220 is formed directly on andin contact with the tunnel barrier layer 218. In other examples, thereis a transitional layer in between the magnetic storage layer 220 andthe tunnel barrier layer 218 that does not affect performance of the MTJstack. The magnetic storage layer is shown in FIG. 2E below.

Further in an embodiment of the MTJ stack 200, a capping layer 222 isformed on the magnetic storage layer 220, and includes a plurality ofinterlayers that form the capping layer 222, including an oxide thatcontains iron (Fe). Additionally, in some embodiments, a hard mask layer224 is formed directly on and in contact with the capping layer 222. Inanother example, the hard mask layer 224 is formed on the capping layer222 with a transitional layer in between the capping layer 222 and thehard mask layer 224; such transitional layer does not affect theperformance of the MTJ stack 200. The hard mask layer 224 may be formedof a metal-oxide, amorphous carbon, ceramics, metallic materials, orcombinations thereof. In one example, the magnetic storage layer 220 isformed directly on and in contact with the capping layer 222. In otherexamples, there is a transitional layer between the magnetic storagelayer 220 and the capping layer 222 that does not affect performance ofthe MTJ stack 200. The capping layer 222 is shown in FIG. 2F below.

FIG. 2B is a magnified view of the buffer layer 204 according toembodiments of the present disclosure. The buffer layer 204 can beformed from tantalum (Ta) or TaN. In another example, which can becombined with other examples, the buffer layer 204 includes a layeredstack of Ta and TaN In other examples that can be combined with examplesherein, the buffer layer 204 includes Co_(x)Fe_(y)B_(z), alone or incombination with Ta, TaN, or a Ta/TaN layered stack. In one example ofthe buffer layer 204, the buffer layer 204 includes at least one bilayer204D. The at least one bilayer 204D includes a first buffer interlayer204A and a second buffer interlayer 204B formed in an alternatingfashion on the substrate 202 for at least one iteration of the at leastone bilayer 204D. In this example, the first buffer interlayer 204A isformed from Ta and the second buffer interlayer 204B is formed from TaN,and the first buffer interlayer 204A is in contact with the substrate202. In another example the first buffer interlayer 204A is formed fromTaN and the second buffer interlayer 204B is formed from Ta, and, thus,TaN is in direct contact with the substrate 202.

In other examples of the buffer layer 204, as shown in FIG. 2A,Co_(x)Fe_(y)B_(z) is used alone for the buffer layer 204 and would thusbe in direct contact with the substrate 202. In another example, asshown in FIG. 2B, a third buffer layer 204C is formed over the at leastone bilayer 204D. In this example, the third buffer layer 204C isfabricated from Co_(x)Fe_(y)B_(z) and formed to a thickness of up to 10Å. Thus, depending upon the configuration of the buffer layer 204, athickness of the buffer layer 204 ranges from 1 Å thick to 60 Å thick.In an example where the third buffer layer 204C Co_(x)Fe_(y)B_(z) isemployed, z is from about 10 wt. % to about 40 wt. %, y is from about 20wt. % to about 60 wt. %, and x is equal to or less than 70 wt. %.

FIG. 2C is a magnified view of the first pinning layer 208 according toan embodiment of the present disclosure. In an embodiment, the firstpinning layer 208 is fabricated from at least one bilayer 230, and whentwo or more bilayers are employed, the two or more bilayers can be saidto form a bilayer stack 234. Each bilayer 230 is fabricated from a firstinterlayer 208A and a second interlayer 208B. The bilayers of the firstpinning layer 208 are expressed as (X/Y)_(n), (208A/208B)_(n), whereeach bilayer is a combination of a first material X and a second,different, material Y, and where n is a number of bilayers in the firstpinning layer 208. In an embodiment, X is Co and Y is one of Pt, Ni, orPd. While n=4 in the example in FIG. 2C, in alternate embodiments, n isfrom 1 to 10. In an embodiment, the at least one bilayer 230 has athickness from about 2 Å to about 16 Å. In one example, the firstinterlayer 208A is formed from Co and is from about 1 Å to about 8 Åthick. The second interlayer 208B can be formed from Pt, Pd, or Ni, orcombinations or alloys thereof, and is from about 1 Å to about 8 Åthick. Further in another embodiment of the first pinning layer 208, theat least one bilayer 230 is formed directly on and in contact with theseed layer 206, and a lattice-matching layer 208C is formed on top ofthe at least one bilayer 230. In an MTJ stack such as the MTJ stack 200in FIG, 2A, the lattice-matching layer 208C is in contact with the SyFcoupling layer 210. In an embodiment, the lattice-matching layer 208C isfrom 1 Å to 3 Å thick. In this example, the lattice-matching layer 208Cis Pt, and in another example, the lattice-matching layer 208C is Pd.Depending upon the embodiment, an overall thickness of the first pinninglayer 208, which may include one or more layers including thelattice-matching layer 208C and, in some examples, the at least onebilayer 230, is from 1 nm to about 18 nm . In other examples, one ormore transitional layers may be formed between the first pinning layer208 and the seed layer 206 that do not negatively affect the propertiesof the MTJ stack.

FIG. 2D is a magnified view of the second pinning layer 212 according toembodiments of the present disclosure. In an embodiment, the secondpinning layer 212 is fabricated from a lattice-matching layer 212A, andthe lattice-matching layer 212A is formed on and contact with the SyFcoupling layer 210. In an embodiment, the lattice-matching layer 212Aincludes a layer of Pt or Pd from 1 Å to 3 Å thick. In one example ofthe second pinning layer 212, at least one bilayer 232 is formed overthe lattice-matching layer 212A. Each bilayer 232 includes a firstinterlayer 212B that can be Co and a second interlayer 212C that can bePt, Ni, or Pd, or combinations or alloys thereof. When two or morebilayers such as the bilayer 232 are employed in the second pinninglayer 212, the two or more bilayers may be referred to as a bilayerstack 236. Thus, when one or more bilayers are deposited at operation138, as show in FIG. 1B, a separate sputtering target may be used toform each of the first interlayer 208A and the second interlayer 208B ofthe bilayer 230. The at least one bilayer 232 of the second pinninglayer 212 is expressed as (X/Y)_(n), (212A/212B)_(n), where n is anumber of bilayers. While n=4 in the example in FIG. 2D, in alternateembodiments, n is from 1 to 5. In an embodiment, the at least onebilayer 232 has a total thickness from about 2 Å to about 16 Å. In oneexample, the first interlayer 212B is a Co layer from about 1 Å to about8 Å thick and the second interlayer 212C is from about 1 Å to about 8 Åthick. In various embodiments, the second interlayer 212C includes Ni,Pt, or Pd or combinations or alloys thereof.

Further in another embodiment, the second pinning layer 212 includes anoverlayer 212D of Co formed on top of the at least one bilayer 232. Inother examples of the second pinning layer 212, no overlayer 212D ispresent. In another example, not shown in FIG. 2D, the overlayer 212D ofCo is formed on the lattice-matching layer 212A. In an embodiment, theoverlayer 212D is from about 1 Å to about 10 Å thick. Depending upon theembodiment, an overall thickness of the second pinning layer 212, whichmay include one or more layers including the at least one bilayer 232 asdiscussed herein, is from 0.3 nm to 15 nm. In some examples, atransitional layer may be employed between the at least one bilayer 232and the second pinning layer 212. In other examples, a transition layercan be formed between the at least one bilayer 232 and the SyF couplinglayer 210. In other examples, a transition layer can be formed betweenthe at least one bilayer 232 and the second pinning layer 212 andbetween the at least one bilayer 232 and the SyF coupling layer 210.Such transition layer(s) do not affect performance of the MTJ stack.

In an embodiment, the first pinning layer 208 and second pinning layer212 each include the same interlayer composition and/or a differinginterlayer thickness. In an alternate embodiment, the first pinninglayer 208 and second pinning layer 212 each include differentcompositions and/or thicknesses. In an embodiment, the first pinninglayer 208 includes at least one bilayer including a first interlayer ofCo and a second interlayer of Pt, and further includes a firstlattice-matching layer of Pt or Pd formed over the at least one bilayer.The first lattice-matching layer of the first pinning layer 208 is incontact with an SyF coupling layer 210 formed from Ir. In this example,the second pinning layer 212 is formed over the SyF coupling layer 210and includes a second lattice-matching layer of Pt or Pd formed incontact with the SyF coupling layer 210. In some examples, the secondpinning layer 212 further includes one or more bilayers formed over thesecond lattice-matching layer. In an embodiment, the one or morebilayers of the second pinning layer 212 include a first interlayer ofCo and a second interlayer of Pt. In another embodiment, the firstpinning layer 208 includes at least one bilayer including a firstinterlayer of Co and a second interlayer of Ni, and further includes afirst lattice-matching layer of Pt or Pd formed over the at least onebilayer such that the first lattice-matching layer is in contact withthe SyF coupling layer 210 formed from Ir. In this example, the secondpinning layer 212 includes a second lattice-matching layer of Pt or Pdformed in contact with the SyF coupling layer 210 and, optionally,includes one or more bilayers formed over the second lattice-matchinglayer. In this example, the one or more bilayers of the second pinninglayer 212 include a first interlayer of Co and a second interlayer ofPt.

FIG. 2E is a magnified view of an example magnetic storage layer 220according to embodiments of the present disclosure. As shown in FIG. 2E,a first magnetic layer 220A of the magnetic storage layer 220 and asecond magnetic layer 220B of the magnetic storage layer 220 are eachfabricated from Co_(x)Fe_(y)B_(z). A third layer 220C fabricated fromTa, Mo, W, Hf, or combinations thereof are disposed therebetween. Thethird layer 220C can contain dopants such as boron, oxygen, or otherdopants. The magnetic storage layer 220 is thus fabricated from threelayers, a first magnetic layer 220A and a second magnetic layer 220B,and a third layer 220C disposed between the first magnetic layer 220Aand the second magnetic layer 220B. The third layer 220C strengthens apinning moment perpendicular to the substrate plane (e.g., a planeperpendicular to the substrate 202), which promotes magnetic anisotropy,a directional dependence of the structure's magnetic properties.

FIG. 2F is a magnified view of an example capping layer 222 according toan embodiment of the present disclosure. A total thickness of thecapping layer 222 is from 2 Å to 120 Å and in some embodiments a totaldesired thickness for the capping layer (e.g., including all interlayersas shown in FIG. 2F) is about 60 Å. In an embodiment, the capping layer222 includes a plurality of interlayers. A first capping interlayer 222Ais fabricated from MgO or another iron-containing oxide formed directlyon the magnetic storage layer 220 to a thickness from about 2 Å to about10 Å. On top of the first capping interlayer 222A, a second cappinginterlayer 222B of Ru, Ir, or combinations thereof is formed to athickness from 1 Å to about 30 Å. In an embodiment, a third cappinginterlayer 222C is optionally formed of Ta on the second cappinginterlayer 222B to a thickness of 1 Å to about 30 Å. Thus, someembodiments of a capping layer 222 do not contain a third cappinginterlayer 222C. In an embodiment, a second capping interlayer 222D isoptionally formed on the third capping interlayer 222C and is formed ofRu, Ir, or combinations thereof to a thickness of up to 50 Å. In variousembodiments, the capping layer 222 includes only the first cappinginterlayer 222A, or the first capping interlayer 222A and the secondcapping interlayer 222B, or the first capping interlayer 222A, thesecond capping interlayer 222B, and a third capping interlayer 222C, orthe first, second, and third capping layers 222A-222C. In someembodiments, transitional layers may be used in between some or all ofthe first capping interlayer 222A, the second capping interlayer 222B,and the third capping interlayer 222C, or may be between the cappinglayer 222 and the magnetic storage layer 220, such that the performanceof the MTJ stack is not negatively impacted by the transitionallayer(s).

The MTJ stacks discussed herein have improved performance afterundergoing processing at temperatures at or above 400° C., at leastbecause of the lattice matching between the first pinning layer and SyFcoupling layer and the lattice-matching between the second pinning layerand the SyF coupling layer The lattice matching between the SyF couplinglayer and each of the first and second pinning layers inhibits roughnessformation at the interface of the SyF coupling layer and the firstpinning layer and at the interface of the SyF coupling layer and thesecond pinning layer. The roughness formation results in a lack offlatness in one or more layers which negatively impacts the performanceof the MTJ stacks. Further, in an example where each of the firstpinning layer and the second pinning layer includes a bilayer, a ratioof a thickness of each interlayer of each bilayer of the first pinninglayer and the second pinning layer can be selected to reduce the dipolefield effect when a magnetic field is applied to the MTJ stack. The MTJstacks fabricated according to embodiments of the present disclosure arethus able to maintain structural integrity as well as desirable magneticand electrical properties subsequent to high temperature processing.

While the foregoing is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A device comprising: a magnetic tunnel junctionstack comprising: a first pinning layer comprising a first bilayer and afirst lattice-matching layer formed over the first bilayer, wherein thefirst lattice-matching layer comprises platinum or palladium; asynthetic anti-ferrimagnetic (SyF) coupling layer in contact with thefirst lattice-matching layer of the first pinning layer; and a secondpinning layer in contact with the SyF coupling layer, wherein the secondpinning layer comprises a second lattice-matching layer comprisingplatinum or palladium, the second lattice-matching layer being incontact with the SyF coupling layer.
 2. The device of claim 1, wherein atotal thickness of the first pinning layer and second pinning layer isfrom 1 nm to 18 nm and a total thickness of the second pinning layer isfrom 1 nm to 18 nm.
 3. The device of claim 1, wherein the firstlattice-matching layer is from 1 Å to 3 Å thick and the secondlattice-matching layer is from 1 Å to 3 Å thick.
 4. The device of claim1, wherein the SyF coupling layer comprises ruthenium, chromium,rhodium, or iridium.
 5. The device of claim 1, wherein the first pinninglayer is in contact with a seed layer formed from at least one ofchromium or platinum, the seed layer being from 1 Å to 100 Å thick. 6.The device of claim 1, wherein the first bilayer comprises a firstinterlayer of cobalt from 1 Å to 7 Å thick and a second interlayer ofplatinum, nickel, palladium, or alloys or combinations thereof, thesecond interlayer being from 1 Å to 8 Å thick.
 7. The device of claim 1,wherein the second pinning layer further comprises a second bilayercomprising a first interlayer of cobalt, the first interlayer being from1 Å to 8 Å thick and a second interlayer of platinum, nickel, orpalladium or alloys or combinations thereof, the second interlayer beingfrom 1 Å to 8 Å thick.
 8. The device of claim 1, wherein the secondpinning layer is from 0.3 nm to 15 nm thick.
 9. The device of claim 1,further comprising: a structure blocking layer in contact with thesecond pinning layer; a magnetic reference layer in contact with thestructure blocking layer; a tunnel barrier layer in contact with themagnetic reference layer; and a magnetic storage layer in contact withthe tunnel barrier layer.
 10. The device of claim 1, wherein a firstlattice constant of the first lattice-matching layer and a secondlattice constant of the second lattice-matching layer are each within+/−4% of a third lattice constant of the SyF coupling layer.
 11. Amagnetic tunnel junction stack, comprising: a first pinning layercomprising a first plurality of bilayers and a first lattice-matchinglayer formed over the first plurality of bilayers, wherein the firstlattice-matching layer comprises platinum or palladium, and wherein eachbilayer of the first plurality of bilayers comprises a first cobaltinterlayer and a second interlayer of platinum, nickel, palladium, oralloys or combinations thereof; a synthetic anti-ferrimagnetic (SyF)coupling layer formed on the first pinning layer; and a second pinninglayer formed on the SyF coupling layer, wherein the second pinning layercomprises a second lattice-matching layer formed on the SyF couplinglayer.
 12. The magnetic tunnel junction stack of claim 11, wherein thesecond pinning layer further comprises and a bilayer formed on thesecond lattice-matching layer and a cobalt layer formed on the bilayer,the cobalt layer being from 1 Å to 10 Å thick.
 13. The magnetic tunneljunction stack of claim 11, wherein the second lattice-matching layercomprises platinum or palladium.
 14. The magnetic tunnel junction stackof claim 11, wherein the SyF coupling layer is from 3 Å to 10 Å thickand comprises ruthenium, chromium, rhodium, or iridium.
 15. The magnetictunnel junction stack of claim 11, further comprising: a structureblocking layer on the second pinning layer, wherein the structureblocking layer comprises at least one of tantalum, molybdenum, ortungsten and is from 1 Å to 8 Å thick; a magnetic reference layer on thestructure blocking layer; a tunnel barrier layer on the magneticreference layer; and a magnetic storage layer on the tunnel barrierlayer.
 16. A magnetic tunnel junction stack, comprising: a buffer layer;a seed layer comprising chromium formed over the buffer layer; a firstpinning layer in contact with the seed layer, wherein the first pinninglayer comprises a first bilayer and a first lattice-matching layerformed over the first bilayer, the first lattice-matching layer beingformed from at least one of platinum or palladium, and wherein the firstbilayer comprises a cobalt interlayer and at least one interlayercomprising platinum, nickel, or palladium; a syntheticanti-ferrimagnetic (SyF) coupling layer formed on the first pinninglayer; a second pinning layer formed on the SyF coupling layer, whereinthe second pinning layer comprises a second lattice-matching layerformed on the SyF coupling layer, wherein the second lattice-matchinglayer comprises platinum or palladium; a structure blocking layer formedon the second pinning layer, wherein the structure blocking layercomprises at least one of tantalum, molybdenum, or tungsten; a magneticreference layer formed on the structure blocking layer; a tunnel barrierlayer formed on the magnetic reference layer; and a magnetic storagelayer formed on the tunnel barrier layer.
 17. The magnetic tunneljunction stack of claim 16, wherein the second pinning layer furthercomprises a second bilayer, wherein the second bilayer comprises a firstinterlayer of cobalt and a second interlayer of platinum, nickel, orpalladium, or alloys or combinations thereof.
 18. The magnetic tunneljunction stack of claim 17, wherein the second pinning layer furthercomprises a layer of cobalt formed over the second bilayer and incontact with the structure blocking layer.
 19. The magnetic tunneljunction stack of claim 16, wherein the SyF coupling layer comprisesruthenium, chromium, rhodium, or iridium, and is from 3 Å to 10 Å thick.20. The magnetic tunnel junction stack of claim 16, wherein the firstbilayer of the first pinning layer comprises a first thickness ratiobetween a thickness of the first interlayer and a thickness of thesecond interlayer, and the second bilayer of the second pinning layercomprises a second thickness ratio between a thickness of the firstinterlayer and a thickness of the second interlayer, wherein the firstthickness ratio is greater than the second thickness ratio.